Photosensor, sensor unit, and object detection apparatus using photosensor

A photosensor which is a sensor capable of detecting light, the photosensor comprising:

• an absorber having an entire surface formed of only one of a metal and a dielectric and configured to absorb incident light;
• and
• means for detecting heat generated by absorption of light by the absorber, wherein the absorber absorbs light that is perpendicularly incident on a surface of the absorber and has a same wavelength as a resonance wavelength of the absorber,
• the surface of the absorber includes a plurality of raised portions that are raised,
• the surface of the absorber has a periodic structure in which the plurality of raised portions are arranged at a predetermined period such that a one-dimensional or two-dimensional lattice pattern is formed,
• in the one-dimensional lattice pattern,
• each of the plurality of raised portions is formed in an elongated manner and is arranged at a first period along a predetermined direction so as to be parallel to each other,
• widths of the raised portions are 0.3 to 0.7 times the first period,
• thicknesses of the raised portions are 0.05 to 0.2 times the first period,
• in the two-dimensional lattice pattern,
• each of the plurality of raised portions is arranged at a second period so as to be set out in a grid,
• widths of the raised portions are 0.3 to 0.7 times the second period,
• thicknesses of the raised portions are 0.05 to 0.2 times the second period, and
• each of a plurality of modes of surface plasmon polaritons or surface phonon polaritons excited by a surface parallel component of light incident on the absorber and a momentum obtained from the lattice pattern and propagating over the surface of the absorber is in a degenerate state when the light incident on the absorber is incident perpendicularly to the surface and a wavelength is the resonance wavelength.